Isopropylidene-5-alkyl malonates

Oxidative coupling occurred in several isopropylidene-5-alkyl malonates (Meldrum s acid derivatives) on treatment with DIB under phase transfer catalysis [34] ... 

Chiral allylic cyclic carbonates such as 551 or 552 undergo excellent regioselective alkylation reactions with soft nucleophiles in the presence of palladium(O) in refluxing THF to provide ( )-allylic alcohols. The reaction of 4-0-benzyl-2,3-isopropylidene-L-threose (167) with the appropriate ylid, followed by deprotection of the isopropylidene ring with acidic resin and cyclic carbonate formation, provides a good overall yield of either 551 or 552. Ring opening with diethyl malonate in the presence of tetrakis(triphenylphosphine)palladium(0) provides in excellent yield the allylic alcohols 553 or 554, where the diastereoselectivity exceeds 99%. This reaction represents an efficient method of 1,3-chirality transfer [180] (Scheme 122). 

Microwaves also provide an easy access to 2-alkyl and 2-aryl-4-quinolones by the addition-elimination reaction of 5-methylthioalkylidene isopropylidene malonates with arylamine, followed by cyclization (Huang et al., 2000). A condensation, addition, cyclization and elimination reactions of aromatic aldehydes, 5,5-dimethyl-l,3-cyclohexandione and isopropylidene malonate afforded a series of 4-aryl-7,7-dimethyl-2, 5-dioxo-l,2,3,4,5,6,7,8-octahydroquinoline and 4-aiyl-7,7-dimethyl-5-oxo-3,4,5,6,7,8-hexahydroconmarin under microwaves only in 3-5 min (Tu et al., 2002). Basic silica gel (NaOH/SiO ) in solvent-free conditions and microwave exposure acts as a very efficient medium for the p-elimination (dehydrosulfe-nylation) of sulfoxides (Moghaddam and Jamshidi, 2001). 

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